The lack of rotating black hole models, which are typically found in nature, in loop quantum gravity (LQG) substantially hinders the progress of testing LQG from observations. Starting with a nonrotating LQG black hole as a seed metric, we construct a rotating spacetime using the revised Newman-Janis algorithm. The rotating solution is nonsingular everywhere and it reduces to the Kerr black hole asymptotically. In different regions of the parameter space, the solution describes (1) a wormhole without event horizon (which, we show, is almost ruled out by observations), (2) a black hole with a spacelike transition surface inside the event horizon, or (3) a black hole with a timelike transition region inside the inner horizon. It is shown how fundamental parameters of LQG can be constrained by the observational implications of the shadow cast by this object. The causal structure of our solution depends crucially only on the spacelike transition surface of the nonrotating seed metric, while being agnostic about specific details of the latter, and therefore captures universal features of an effective rotating, nonsingular black hole in LQG.

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从非奇异旋转黑洞的观测结果测试环路量子引力

循环量子引力（LQG）中缺乏自然界中通常发现的旋转黑洞模型，这严重阻碍了从观察中测试LQG的进展。从非旋转LQG黑洞作为种子度量开始，我们使用修订的Newman-Janis算法构造旋转时空。旋转解在任何地方都是非奇异的，并且渐近地减小到Kerr黑洞。在参数空间的不同区域中，该解决方案描述了（1）没有事件视界的虫洞（我们证明，观测结果几乎排除了虫洞），（2）在事件视界内具有空间过渡表面的黑洞，或者（3）一个黑洞，其内部视界内部具有类似时间的过渡区域。它显示了LQG的基本参数如何通过此对象投射的阴影的观察影响来约束。我们解决方案的因果结构主要取决于非旋转种子度量的类空过渡表面，而对后者的具体细节不可知，因此可以捕获LQG中有效旋转的非奇异黑洞的普遍特征。